Portable electronic devices are used in environments where hands-free interaction would be desirable. For example, on construction sites or in warehouses, a user benefits from manipulating objects while still having interaction with an electronic device, such as a mobile computer. Moreover, portable electronic devices typically have compact displays, often measuring only several inches across, or less. Visualizing information on a small display can be limiting both in the total amount of information displayable as well as the increased concentration required by a user to focus on minute graphical images.
Wearable computing devices are sometimes used to allow a user to receive information without the need to carry a separate device. Additionally, such computing devices can include a head-mounted display which presents a screen near the eye of the user. The proximity of the screen to the user's eye, as well as the use of magnifying optics, can result in a screen perceived to be much larger than the actual size of the screen. Because the overall size of the screen appears larger, more information can be displayed at a size easily viewable by the user when a relatively high-resolution screen is used. Such head-mounted displays can be used with non-wearable computing devices as well, with the same benefit.
Head-mounted displays can be cumbersome, heavy, and uncomfortable to wear. Head-mounted displays are typically supported by a bulky, rigid structure passing over the top of the user's head. Such a structure has other drawbacks, including the lack of compatibility with equipment typically used in situations where a head-mounted display is desirable. For example, on a construction site, a user might be required to wear a hard hat or safety glasses. Typical head-mounted displays often inhibit the wearing of such devices.